In order electrically to interconnect insulated conductors in certain kinds of environments such as, for example, in splice cases or in telephone central offices, slotted beam connectors are used. These connectors, commonly known as contact elements, have a central body with beams extending bilaterally therefrom. Each beam is bifurcated with the furcations of each beam being spaced apart to define a conductor-receiving slot having predetermined width characteristics. See, for example, U.S. Pat. No. 4,136,628 issued Jan. 30, 1979 in the names of Charles McGonigal and James Emery Voytko.
A connection between two insulated conductors is made by the insertion of one of the conductors into the slot in one of the beams and the other conductor into the slot in the other one of the beams. As this is done, portions of the connector which define flared entrances to the slots slice through the insulation and cause an electrical connection to be established between the contact element and the conductor.
Corrosion at the interface of the conductor and the walls of the beam which define the conductor-receiving slots is prevented by a resistant material which is plated on those walls, but a problem arises because an average width of each of the conductor-receiving slots may be on the order of only several mils, and a specified minimum plating thickness is required on the walls which define each slot. Because they are not well exposed to an electroplating electrolyte and an electric field when using conventional plating methods, the surfaces which define a conductor-receiving slot are commonly said to be less significant surfaces or low current density areas compared to significant surfaces or high current density areas such as flat, parallel major surfaces of the contact element. Inasmuch as the slot width is relatively small, excessive plating on other surfaces may ensue, particularly on ends of the beam, if conventional techniques in which a strip is indexed into a plating station, masked and plated are used to achieve the minimum thickness required on the slot walls.
It is not required nor is it desirable to plate some surface areas of the contact elements, such as for example, the ends of the beam which define entrance portions of the slots since the conductors engage those walls only temporarily as they are used to slice through or otherwise penetrate the conductor insulation. While soft metals such as, for example, solder, are especially suitable for the extablishment of electrical contact with a conductor, their use as the plating metal inhibits insulation penetration and may prevent the establishment of electrical contact between the slot walls and the conductor. Also, the unwanted deposition of plating material on the flat, parallel surfaces of the contact element causes a problem during manufacture as the strip of metal is indexed through and formed partially at each of a plurality of work stations as well as in subsequent operations where the element is assembled into a connector unit. Soft plated materials tend to adhere to portions of work tools at each station as the tools are moved out of engagement with flat surfaces of the strip thus impairing the indexing of the strip and increasing tool maintenance.
In U.S. Pat. No. 4,033,833 issued July 5, 1977 in the names of J. L. Bestel et al, an anode is contact-masked with a dielectric member to shield the anode from a spaced, charged surface after which electroplating electrolyte is distributed over at least the area to be electroplated. The prior art also includes U.S. Pat. No. 2,974,097 in which a strip is advanced between spaced ribs that cooperate to seal a center portion of the strip from a longitudinal edge of the strip which together with an anode protrude from opposite walls into a chamber which is filled with an electrolyte. Other prior art arrangements are shown in U.S. Pat. Nos. 3,470,081, 3,723,283, 3,962,063, 4,033,832 and 4,048,043.
It is also desirable in continuous strip plating to be able to advance the strip at a relatively high speed and to contact it with an electrolyte having a relatively high turnover. Moreover, the parameters which affect the flowing electrolyte should be capable of being controlled independently of the ratio of surface area of the anode and the exposed portions of the strip. The prior art includes Tezuka et al U.S. Pat. No. 4,029,555, but it includes a nozzle anode which does not allow independent control of parameters and also employs an angled flow passage which results in cavitation.
These prior art arrangements are not satisfactory for the plating of the cnductor-receiving slot walls which extend between the parallel major surfaces of a continuously moving strip of contact elements. What is needed and what the prior art lacks is a mask and anode arrangement and an electrolyte flow pattern in which the slot walls of the bifurcated beams are converted from less significant to more significant surfaces so that a minimum plating thickness of the slot walls is achieved without the deposition of an excessively thick plating on other functional or non-functional surfaces. A plating arrangement which overcomes the problems of the prior art should also be one which is capable of plating the slot walls with a metal which is not only electrically conductive but one which is also capable of penetrating any one of a number of commonly used conductor insulation materials.